An image sensor with dual power supply of 1.8V and 1.1V is proposed. The sensor works on blocks of 88 pixels and the power supply for each block is selected according to the estimated variance inside the block. For the blocks with large variance, 1.8V is chosen to achieve high imaging performance; otherwise, 1.1V is used to save power. Preliminary evaluation of the imager performance based on simulations for TSMC 0.18 m CMOS technology is given. The estimated amount of power saved by the proposed imager varies from image to image. Theoretically, up to 37% of power can be saved for images with predominant background, while no noticeable quality degradation of the reconstructed pictures after compression and decompression is perceived (PSNR reduced by less than 1.5 dB).